The invention relates to a process for manufacturing tapes or yarns, to a die and to a system for use in that process.
A known process for manufacturing tapes and yarns of polymer material is to extrude the material in the form of a film, to draw the film in the direction of extrusion and to divide the film longitudinally into tapes or strands. As for most other type of yarn or tape, a major objective in the development of yarns and tapes of this type is generally to achieve a maximal tensile strength.
One known process step contributing to increasing the tensile strength is to draw the extruded material, usually while submitting it to a heat treatment, so that polymer chains in the material are aligned in longitudinal direction.
AU-B1-30,204/7 discloses a process in which a plastic polymer material is extruded into a film having a pattern of parallel, longitudinal, alternating ribs and grooves on each of its two opposite sides. The grooves in one side each are located diametrically opposite one of the grooves in the other, opposite side. The grooves are formed using a die having opposite die lips both provided with projecting groove-forming protrusions, the groove-forming protrusions of opposite lips being located diametrically opposite each other. The extruded film is longitudinally cleaved in production (the tape may also cleave in use if heavily loaded), by slitting between ridges. Furthermore, this document discloses a die for extruding a drawable film of polymer material, which die has an extrusion gap between generally parallel, mutually spaced, opposite lips. The lips each have a toothed profile formed by alternating groove-forming protrusions and recesses for extruding a film as described. The recesses in one lip are each located diametrically opposite one of the recesses in the other, opposite lip. A film as described is also disclosed in this document.